In recent years, connector technology has not kept pace with the solid state circuit technologies. As the solid state chips have become capable of supporting more and more complicated circuit patterns, the input-output densities, (i.e., the fine signal wires that are necessary to communicate one circuit chip to another, usually given in the number of input-output circuits per cubic inch) are also increasing exponentially. As the density of input-output circuits increase, the maintenance and parts damage percentage have gone up and connectors have now become one of the least reliable components within electronic subsystems.
To put the problem in perspective during the vacuum tube era where considerable power was required for the vacuum tubes, it was common practice to have the complete circuit subassembly serviced by a large cable with a relatively large connector with 1/16th inch diameter pins. With the advent of circuit compression through solid state electronics these requirements have now risen to a point where it is not uncommon for a single connector to have 150, 0.30 inch diameter contacts. With this high density of small pins, it is very easy to have one or more of the pins become deflected and/or mate improperly causing poor contact or making the connector unusable. This is why connector failures have become one of the dominate failure modes in avionic equipment.
The principal way of avoiding these pin chrunching connector joining operations is to use what is commonly called a zero insertion force (ZIF) connector. In this type of connector the pins and sockets are joined without any contact of the mating surfaces themselves so that very little insertion force is necessary. With the two halves joined, a latch or cam mechanism is operated to engage all of the contacts and complete the circuit. These ZIF connectors have become very popular and sometimes very exotic. An example of zero insertion force connectors can be found in U.S. Pat. No. 4,517,625 "Circuit Board Housing with Zero Insertion Force Connector" by A. Frink et al. But even these ZIF connectors rely on a spring force to maintain contact during the vibration and shock loads encountered during operation which limits reliability.
Furthermore, certain applications do not lend themselves to use of zero insertion force connectors. For example, in integrated circuit board racks the back planes, to which the numerous circuit boards are connected to, and are located deep within the mounting cabinet where activation of a ZIF connector is impractical.
The only required interfacing of back plane segments in the past, was accomplished by using conventional connectors having hundreds of contacts, each a potential failure point. Existence of these potential points of failure resulted in a high risk condition and lowering of reliability of the back plane. An alternate method is to hard wire the back plane segments in place, but this has not been an acceptable alternative in many applications. Furthermore, field repair would be a nightmare, for the technicians are not likely to be skilled in soldering techniques nor are proper soldering tools likely to not be available.
Applicant's U.S. Pat. No. 4,723,924, "Resolderable Electrical Connector", is considered pertinent in that it provided the advantages of "hard wiring" and high density contacts. In detail, this invention comprised a first connector half having a first set of electrical contacts and a second connector half having a second set of electrical contacts. At least one of the first and second sets of electrical contacts is coated or tinned with solder. An integral heater is coupled to the first electrical connector for heating the solder to a temperature wherein the solder can be melted. Thus, the connector halves can be connected such that the first and second sets of electrical contacts are in contact. Thereafter, the contacts can be heated by applying electrical current to the heater so that the solder is "reflowed". When the electrical power is terminated the solder solidifies, thus forming a continuous and air tight path between the first and second sets of contacts. To separate the connector halves, electrical power is again applied to the heater to melt the solder and, thereafter the connector halves can be manually separated.
Thus, it is a primary object of the subject invention to provide an electrical connector that has increased reliability.
It is another primary object of the subject invention to provide an electrical connector that obtains the advantages of hard wiring while being easily separated.
A further object of the subject invention is to provide an electrical connector that is not subject to deterioration of the electrical contacts due to corrosion.
A still further object of the subject invention is to provide an electrical connector which substantially prevents the deteriorating of electrical contact with time.
Another object of the subject invention is to provide a method of mating contacts of electrical connectors that is not subject to contact separation due to vibrations, shock or accelerator loads.
An additional object of the subject invention is to provide an electrical connector with extremely high contact density.